Vacuum tube



H. LEMS VACUUM TUBE Nov. 21, 1933.

Filed Oct. 5, 1931 Inventor: Hendrick Lems,

His Attorneg PATENT OFFICE VACUUM TUBE Hendrik Lems, Eindhoven, Netherlands, assignor to General Electric Company, a corporation of New York Application October 5, 1931, Serial No. 566,887, and in Germany October 9, 1930 3 Claims. (Cl. 250-275) The invention relates to vacuum tubes comprising a wall portion consisting of refractory material and sealed by means of a graded seal consisting of several rings to another wall portion. The composition of these intermediary rings is, as is well known, so chosen that the coefficients of expansion of the difierent rings are the higher the farther remote the rings are from the refractory material.

Such vacuum tubes are frequently employed, for example, for the generation of ultra-violet rays. A portion of the wall of the tubes often consists for this purpose of quartz or any other refractory material transparent to ultra-violet rays. This wall portion is sealed in this case with the aid of intermediary rings to a wall portion which consists of ordinary glass and through which the current supply wires may be led. These tubes may be provided with two or more electrodes and with a suitable gasfilling consisting of one or more gases, one or more vapors or a mixture of gas and vapor. Mercury vapor is mostly utilized for the filling of vapor. The composition of the filling is so chosen in this case that an electric discharge established in the discharge tube generates ultra-violet rays which may emerge from the tube through the wall portion consisting of quartz or like material. It is also possible to generate the ultra-violet rays by heating a tungsten filament to a very high temperature.

According to the invention, the graded seal is coated on the outside with an opaque layer, for example of opalescent glass. This layer not only protects the graded seal but also conceals it from view so that the tube has a more pleasant appearance. In many cases the opaque layer impedes the radiation of heat owing to which, for example, the advantage may be obtained that the metal vapor present in the tube acquires a higher pressure.

The invention will be more clearly understood by referring to the accompanying drawing which represents, by way of example, a vacuum tube according to the invention suitable for the emission of ultraviolet rays. In this drawing:

Figure 1 represents a section,

Figure 2 an elevation of this tube, and

Figure 3 shows a form where the glass upper portion is transparent.

The tube represented in the drawing comprises a bulb 1 of quartz sealed to a foot 3 by means of a graded seal consisting of some intermediary rings 2. This foot carries the electrodes of the tube which are constituted by concentric gauzeshaped cylinders but which may also be of any other construction. The tube contains some mercury and some argon, for example at a pressure of some millimeters. When a discharge is established between the electrodes of the tube, the mercury vapor discharge generates ultraviolet rays which pass to the outside through the quartz wall and which may form ozone from the surrounding air.

The current supply wires of the electrodes pass through the foot 3 which is made for this purpose of a material whose coefficient of expansion is greater than that of quartz. The use of the intermediary rings 2 allows of establishing an airtight joint between the foot 3 and the quartz bulb 1.

The intermediary rings 2 are coated with. a layer 4 of opalescent glass which is opaque and therefore conceals the intermediary rings from view. The tube is provided with a cap 5 consisting of insulating material, for example of artificial resin and provided with two contact pins 6 with the aid of which current may be supplied to the electrodes of the tube. Between one of the pins and one electrode of the tube is connected a resistance 7 which is schematically shown in Figure 1. This resistance may consist,- for example, of resistance wire and be housed in the cap 5 or in the foot 3.

It will be evident that the cap 5 may also be constructed in other ways. The cap may be provided, for example with three pins, as shown in Fig. 3, owing to which a rigid mounting in the valve-holder is rendered possible. It is also possible to provide the discharge tube with an Edisoncap owing to which the tube may be mounted in an ordinary threaded fitting.

What I claim is:

1. A vacuum tube having a wall portion of refractory material which is sealed by means of a graded seal to the basal portion of said tube, said seal being coated on the outside with an opaque opalescent glass layer.

2. An electric discharge device comprising a container, electrodes sealed therein, a gaseous discharge supporting atmosphere therein, one portion of said container having a definite coefficient of expansion and being joined to another portion of said container by a graded-seal, said last-named portion having a different coefiicient of expansion than said first-named portion, said seal having an opaque glass coating on the outer wall thereof.

3. An electric discharge device comprising a container, electrodes sealed therein, a gaseous discharge supporting atmosphere therein, one portion of said container having a definite coefflcient of expansion and being joined to the stem part of said container by a graded seal, said stem part having a different coeiiicient of expansion than said container portion, said seal having an opaque glass sleeve fused on the outer wall thereof, said sleeve having a base mounted thereon.

HENDRIK LEMS. 

